In the pilot, the Huxtables have only four children. Following the pilot, the Huxtables have five children, with the addition of their eldest daughter, Sondra (Sabrina Le Beauf). The character was created when Bill Cosby wanted the show to express the accomplishment of successfully raising a child (e.g., a college graduate).Whitney Houston was considered for the role of Sondra Huxtable. Sabrina LeBeauf almost missed out on the role because she is only 10 years younger (b. 1958) than Phylicia Rashād (b. 1948), who played her mother.

Bill Cosby’s character is called “Clifford” in the early episodes of the first season (as evidenced by his name plate on the exterior of the Huxtable home). His name was later switched to “Heathcliff”. Additionally, Vanessa refers to Theo as “Teddy” twice in the dining room scene.

(via Wikipedia)